International Ocean Discovery Program Expedition 363 Scientific Prospectus Western Pacific Warm Pool Neogene and Quaternary records of Western Pacific Warm Pool paleoceanography Yair Rosenthal Ann Holbourn Co-Chief Scientist Co-Chief Scientist Department of Marine Sciences and Earth Institute of Geosciences and Planetary Sciences Christian-Albrechts Universität zu Kiel Rutgers, the State University of New Jersey Ludewig-Meyn-Strasse 10-14 71 Dudley Road D-24118 Kiel New Brunswick NJ 08901 Germany USA Denise Kulhanek Expedition Project Manager/Staff Scientist International Ocean Discovery Program Texas A&M University 1000 Discovery Drive College Station TX 77845 USA Publisher’s notes This publication was prepared by the International Ocean Discovery Program JOIDES Resolution Science Operator (IODP JRSO) as an account of work performed under the International Ocean Discovery Program. Funding for the program is provided by the following implementing organiza- tions and international partners: National Science Foundation (NSF), United States Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan European Consortium for Ocean Research Drilling (ECORD) Ministry of Science and Technology (MOST), People’s Republic of China Korea Institute of Geoscience and Mineral Resources (KIGAM) Australian-New Zealand IODP Consortium (ANZIC) Ministry of Earth Sciences (MoES), India Coordination for Improvement of Higher Education Personnel, Brazil (CAPES) Portions of this work may have been published in whole or in part in other International Ocean Discovery Program documents or publications. This IODP Scientific Prospectus is based on precruise JOIDES Resolution Facility advisory panel discussions and scientific input from the designated Co-Chief Scientists on behalf of the drilling proponents. During the course of the cruise, actual site operations may indicate to the Co-Chief Scientists, the Staff Scientist/Expedition Project Manager, and the Operations Superintendent that it would be scientifically or operationally advantageous to amend the plan detailed in this prospectus. It should be understood that any proposed changes to the science deliverables outlined in the plan presented here are contingent upon the approval of the IODP JRSO Director. Disclaimer Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the participating agencies, Texas A&M University, or Texas A&M Research Foundation. Copyright Except where otherwise noted, this work is licensed under a Creative Commons Attribution License. Unrestricted use, distribution, and reproduction is permitted, provided the original author and source are credited. Citation Rosenthal, Y., Holbourn, A., and Kulhanek, D.K., 2016. Expedition 363 Scientific Prospectus: Western Pacific Warm Pool. International Ocean Discovery Program. http://dx.doi.org/10.14379/iodp.sp.363.2016 ISSN World Wide Web: 2332-1385 February 2016 Y. Rosenthal et al. Expedition 363 Scientific Prospectus Abstract only in the tropics but also in many regions around the world; El Niño events are associated with a nearly global fingerprint of tem- Expedition 363 seeks to document the regional expression of cli- perature and precipitation anomalies (Ropelewski and Halpert, mate variability (e.g., temperature, precipitation, and productivity) 1987; Rasmusson and Arkin, 1993; Cane and Clement, 1999). in the Western Pacific Warm Pool (WPWP) as it relates to global Considerable uncertainty exists regarding the response of the and regional climate change from the middle Miocene to Late Pleis- tropical Pacific climate, primarily precipitation, to rising green- tocene on millennial, orbital, and secular timescales. The WPWP is house gases because of our limited understanding of past variability the largest reservoir of warm surface water on Earth and thus is a of the WPWP and conflicting data-model results. For example, major source of heat and moisture to the atmosphere. Variations in models simulating the response of the equatorial Pacific to green- sea-surface temperature and the extent of the WPWP influence the house gas forcing disagree about whether the zonal temperature location and strength of convection and thus impact oceanic and at- gradient will increase or decrease and what the implications will be mospheric circulation, heat transport, and tropical hydrology. for the Walker circulation and the hydrologic cycle in the tropics. Given its documented importance for modern climatology, changes These simulations typically use an ENSO analogy to predict future in the WPWP are assumed to have also played a key role in the past. climate, with the idea that changes in ENSO variation are intimately The proposed drill sites are strategically located at the heart of the linked to long-term changes in the equatorial Pacific mean climate WPWP (northern Papua New Guinea and south of Guam) and state as expressed in the east–west SST gradient. However, recent around its western edge (western margin of Australia to the south simulations of global warming effects suggest that the tropical Pa- and southern Philippine Islands to the north) to capture the most cific does not become more El Niño- or La Niña-like in response to salient features of the WPWP. Combining marginal and open ocean increased greenhouse gases (DiNezio et al., 2009). Instead, the new sites will allow us to study these time intervals at different temporal simulations suggest a different equilibrium state, whereby shoaling resolutions. The coring program prioritizes seven primary sites and and increased tilt of the equatorial Pacific thermocline is associated nine alternate sites in 880–3427 m water depth. This depth range with weakening of the trade winds without a concomitant change in will allow the reconstruction of intermediate and deepwater prop- the zonal SST pattern, which is a departure from the ENSO analogy erties through time. (DiNezio et al., 2010). In turn, changes in the structure of the ther- mocline can have a major effect on the ocean heat content and thus Schedule for Expedition 363 global climate, which has been documented for the Last Glacial Maximum (LGM) (Ford et al., 2015) and is also suggested to explain International Ocean Discovery Program (IODP) Expedition today’s climate trends (e.g., England et al., 2014). A primary goal of 363 is based on IODP drilling Proposals 799-Full2 and 799-Add this expedition is to assess the regional expression of climate vari- (available at http:// iodp.tamu.edu/ scienceops/ expeditions/ ability (precipitation and temperature) within the WPWP in the pacific_warm_pool.html). Following ranking by the IODP Scien- context of changing global background state from the middle Mio- tific Advisory Structure, the expedition was scheduled for the re- cene to Late Pleistocene. Drill sites have been chosen to provide search vessel R/V JOIDES Resolution, operating under contract broad spatial coverage to capture the most salient features of the with Texas A&M University. At the time of publication of this Sci- WPWP (Figures F1, F2) at different temporal resolutions from the entific Prospectus, the expedition is scheduled to start in Singa- late Neogene to the present (Figure F3). At depth, these sites are pore on 6 October 2016 and to end in Guam on 8 December bathed by Antarctic Intermediate Water (AAIW) and Upper Cir- (Figure F1). A total of 63 days will be available for the transit, drill- cumpolar Deepwater (UCDW) (Figure F4) and thus will allow the ing, coring, and downhole measurements described in this report reconstruction of intermediate and deepwater end-member proper- (for the current detailed schedule, see http://iodp.tamu.edu/sci- ties through time and at relatively high resolution. enceops/). Further details about the facilities aboard the JOIDES The causes and extent of past precipitation changes in the Resolution can be found at http://iodp.tamu.edu. WPWP are not well constrained in terms of the relative importance of extra-tropical controls, such as the position of the ITCZ versus Introduction equatorial Pacific dynamics, which affect the SST pattern and loca- tion of maximum convection (Figure F5). Paleo-precipitation re- The Indo-Pacific Warm Pool (IPWP) is the largest source of heat cords suggest a southward shift in the ITCZ position apparently for the global atmosphere and a location of deep atmospheric con- synchronous with North Atlantic cold events including the Younger vection and heavy rainfall. Small variations in the sea-surface tem- Dryas, Heinrich Event 1, and marine isotope stage (MIS) 3 stadials perature (SST) of the Western Pacific Warm Pool (WPWP), within (Stott et al., 2002, 2004; Oppo et al., 2003; Dannenmann et al., 2003, the IPWP, influence the location and strength of convection in the Gibbons et al., 2014). These results are consistent with models that rising limbs of the Hadley and Walker circulations, perturbing plan- suggest climate conditions at high latitudes influence the position of etary-scale atmospheric circulation, atmospheric heating globally, the ITCZ (Broccoli et al., 2006; Chiang and Bitz, 2005). However, and tropical hydrology (Neale and Slingo, 2003; Wang and Mehta, lithologic records of chemical weathering (e.g., Ti/Ca) from Mind- 2008). Seasonal to interannual climate variations in the WPWP are anao and northern Papua New Guinea (PNG), which are used as a dominated by fluctuations in precipitation associated with the sea- precipitation proxy (Kissel